In the applicant's co-pending patent application entitled “Frame Based Data Transmission Over Synchronous Digital Hierarchy Network”, there is disclosed a method of carrying frame based data over a synchronous digital network, such as a synchronous digital hierarchy (SDH) network or the US counterpart “SONET” network. The applicant's aforementioned disclosed system may provide OSI layer 2 switching functionality (which was only previously available in prior art local area networks) extended over a geographical coverage area which has been historically considered to have been provided only by a prior art wide area network.
In order to accommodate data communications frame based data, which is characterised by its own set of data rates and control data characteristics, and to contain such frame based data in conventional synchronous digital networks, there is a problem that the frame based data communications data rates are not well matched to conventional telecommunication data rates, for example E1, E3, T1, STM-1 data rates. These standard telecommunications interfaces are used by the data communications industry to provide wide area networks formed from point to point links. However, this is inconvenient for data communications service providers since data communications protocols have developed using a completely different set of interfaces and protocols, for example carrier sense multiple access collision detection (CSMA/CD) systems, subject of IEEE standard 802.3, such as the Ethernet which is available in 10 MegaBits/s, 100 megabits/s and 1 gigabits/s versions. Conventional data communications protocols do not match up very well to conventional telecommunications interfaces because of a mismatch in data rates and technologies between conventional data communications and conventional telecommunications.
Several prior art attempts have been made to carry frame based data over telecommunications networks, and are briefly summarized in the applicant's aforementioned co-pending patent application. However, prior art schemes suffer from various disadvantages such as, in certain schemes, a substantial packetization header overhead, which can comprise up to 20% of an SDH packet payload.